Explosive booster

Abstract

An explosive booster for initiating, and thus causing detonation of, a bulk explosive, includes a hollow body comprising a base member and a sidewall projecting from the base member. The body defines an interior space between the base member and the sidewall for containing a detonable booster formulation in use. A hollow elongate initiator locating formation projects longitudinally into the interior space at least from the base member and defines an initiator channel that is open through the base member, for locating an explosive initiator in initiating proximity relative to a detonable booster formulation contained in the interior space in use. The initiator channel extends longitudinally along a central longitudinal axis thereof that is radially spaced from, and parallel to, a central longitudinal axis along which the interior space longitudinally extends.

The invention claimed is: 
     
       1. An explosive booster for initiating, and thus causing detonation of, a bulk explosive, the booster including
 a hollow body comprising a base member and a sidewall projecting from the base member, the body defining an interior space between the base member and the sidewall for containing a detonable booster formulation in use; 
 a hollow elongate initiator locating formation that projects longitudinally into the interior space at least from the base member and that defines an initiator channel that is open through the base member, for locating an explosive initiator therein and thus in initiating proximity relative to a detonable booster formulation that is contained in the interior space in use, 
 
       wherein the initiator channel extends longitudinally along a central longitudinal axis thereof that is radially spaced from and parallel to a central longitudinal axis along which the interior space longitudinally extends,
 wherein the body defines a mouth at which the interior space terminates and through which a detonable booster formulation may be loaded into the interior space in use, the mouth thus providing a distal end of the interior space, the booster further including a removable closure member that is of a material different to the material of the body and is configured such that the closure member is mountable to the body to close the mouth, and 
 wherein the closure member and the body have complementary thread formations that are threadable to screw the closure member onto the body, thus mounting the closure member on the body and closing the mouth, the complementary thread formations being configured for effecting liquid tight mounting of the closure member to the body by threading engagement of the complementary thread formations through two revolutions of the closure member about a screw axis that co-extends with the central longitudinal axis of the interior space; and 
 the closure member comprises a channel formation within which a part of the body that defines the mouth is seated when the closure member is screwed onto the body. 
 
     
     
       2. The explosive booster according to  claim 1 , wherein the initiator locating formation extends along, and is thus connected to, the sidewall along at least a part of length of the locating formation, such that the initiator locating formation interfaces with the sidewall and such that that a part of the initiator locating formation therefore comprises, or is comprised by, the sidewall. 
     
     
       3. The explosive booster according to  claim 1 , wherein the interior space and the initiator channel have each have a circular cross-sectional outline that is substantially constant along their respective lengths. 
     
     
       4. The explosive booster according to  claim 1 , wherein
 the interior space has a diameter of at least about 40 mm, more preferably at least about 50 mm, most preferably at least about 60 mm; 
 the interior space extends along a length of from about 93 mm; 
 the base member has a thickness of from about 1.5 mm; 
 the initiator locating channel has a length sufficient to locate therein, and more specifically in a part thereof that is located inside the interior space, an elongate initiator that has a length of from about 55 mm to about 100 mm; 
 walls of the initiator locating formation that are located inside the interior space and that do not interface with the sidewall have a thickness of from about 0.6 to about 0.99 mm. 
 
     
     
       5. The explosive booster according to  claim 4 , wherein the initiator locating channel has a length of about 113.50 mm. 
     
     
       6. The explosive booster according to  claim 1 , wherein the initiator locating formation terminates at a distal end thereof that comprises a distal end wall that is located inside the interior space, which distal end wall is spaced from a distal end of the interior space at a spacing of at least 20 mm. 
     
     
       7. The explosive booster according to  claim 1 , wherein the distal end wall has a thickness greater than that of the walls of the initiator locating formation that are located inside the interior space and that do not interface with the sidewall. 
     
     
       8. The explosive booster according to  claim 1 , which includes a lacing formation defining an elongate lacing channel extending along a side of the body, outside of the interior space, longitudinally along a lacing axis that is parallel to both the central longitudinal axis of the interior space and the central longitudinal axis of the initiator channel, through and along which to lace shock signal propagating means in use and thus connect such shock signal propagating means to the booster in use. 
     
     
       9. The explosive booster according to  claim 8 , wherein, other than at interfaces with the initiator locating formation and lacing formation respectively, the sidewall of the body has a thickness of from about 2 mm to about 3.5 mm. 
     
     
       10. The explosive booster according to  claim 1 , which includes a mounting member atop the closure member, wherein the mounting member defines a gripping axis and is configured to grip detonation signal propagating means such that the detonation signal propagating means extends along the gripping axis. 
     
     
       11. The explosive booster according to  claim 10 , wherein the lacing formation
 is located such that the lacing axis is angularly spaced from the central longitudinal axis of the initiator channel about the central longitudinal axis of the interior space and also radially spaced from the central longitudinal axis of the initiator channel along radii of the central longitudinal axis of the interior space; 
 extends along, and is thus connected to, the sidewall along at least a part of the length of the lacing formation, such that the lacing formation interfaces with the sidewall with and a part of the lacing formation therefore comprising, or being comprised by, the sidewall. 
 
     
     
       12. The explosive booster according to  claim 10 , wherein the location of the mounting member atop the closure member is such that, when the closure member has been screwed onto the body to close the mouth liquid-tightly, the mounting member is radially spaced from the screw axis such that the gripping axis perpendicularly intersects the screw axis and the lacing axis respectively. 
     
     
       13. A loaded explosive booster comprising
 an explosive booster according to  claim 1 , and 
 a detonable booster formulation in the interior space of the body of the explosive booster, 
 wherein the body of the explosive booster is closed liquid-tightly with the closure member. 
 
     
     
       14. The loaded explosive booster according to  claim 13 , wherein the interior space of the body is partially filled with the detonable booster formulation, such that there is air inside the interior space of the body in addition to detonable booster formulation. 
     
     
       15. The loaded explosive booster according to  claim 13 , wherein the detonable booster formulation is a sodium perchlorate-based, formulation. 
     
     
       16. A blasting assembly comprising
 a loaded explosive booster according to  claim 13  which includes a mounting member atop the closure member, wherein the mounting member defines a gripping axis and is configured to grip detonation signal propagating means such that the detonation signal propagating means extends along the gripping axis, wherein the location of the mounting member atop the closure member is such that, when the closure member has been screwed onto the body to close the mouth liquid-tightly, the mounting member is radially spaced from the screw axis such that the gripping axis perpendicularly intersects the screw axis and the lacing axis respectively; 
 detonation signal propagating means gripped by the mounting member and laced through the lacing channel of the explosive booster such that the detonation signal propagating means extends along the gripping and lacing axes; and 
 an explosive initiator located in the initiator channel, to which initiator the detonation signal propagating means is operatively connected. 
 
     
     
       17. A method of blasting earth or rock, the method including
 locating a blasting assembly according to  claim 16  in initiating proximity to a bulk explosive in a body of earth or rock to be blasted; and 
 causing the initiator of the loaded explosive booster to detonate the detonable booster formulation and, thus, the bulk explosive, by communicating a detonation signal to the initiator along the detonation signal propagating means.